Search Results (54)

The study of Ultra-High-Energy Cosmic Rays is made possible by space telescopes that allow for the recording of signals generated by Extensive Air Showers (EAS) on the night side of the Earth’s atmosphere. One of the requirements for these telescopes is the detection of very low photon fluxes, achievable using the latest generation SiPMs characterized by high intrinsic gains, low power consumption, low weight, and robustness against accidental exposure to light. Despite these advantages, some technological issues still need to be addressed, such as the radiation hardness for operation in space. Therefore, the design of a SiPM-based focal surface for UHECR detection must consider the space qualification of SiPM arrays, with the development of compact arrays optimized for low dead-area focal surfaces. SiSMUV (SiPM-based Space Monitor for UV light) is a project dedicated to developing a compact and modular UV detector for use in space telescopes designed to study the fluorescence and Cherenkov signals produced by Ultra-High-Energy Cosmic Rays (UHECRs). Each SiSMUV module incorporates a matrix of SiPMs, a readout ASIC (Radioroc by Weeroc), and an FPGA into a monolithic block. This design enables the acquisition and processing of signals from the sensors. The system can connect to a PC for standalone operation or with back-end electronics for integration into more complex systems. In this paper, we will describe the prototype electronics, the experimental setup and the measurements performed to obtain parameters such as the gain of the SiPMs, and their photon detection efficiency (PDE). We will also present the firmware developed to interface with the readout ASIC and to transmit data to other peripherals. Full article

Automatic speech recognition in a scenario with multiple speakers in a reverberant space, such as a small courtroom, often requires multiple sensors. This leads to a problem of crosstalk that must be removed before the speech-to-text transcription is performed. This paper presents an algorithm intended for application in multi-speaker scenarios requiring speech-to-text transcription, such as court sessions or conferences. The proposed method uses Acoustic Vector Sensors to acquire audio streams. Speaker detection is performed using statistical analysis of the direction of arrival. This information is then used to perform source separation. Next, speakers’ activity in each channel is analyzed, and signal fragments containing direct speech and crosstalk are identified. Crosstalk is then suppressed using a dynamic gain processor, and the resulting audio streams may be passed to a speech recognition system. The algorithm was evaluated using a custom set of speech recordings. An increase in SI-SDR (Scale-Invariant Signal-to-Distortion Ratio) over the unprocessed signal was achieved: 7.54 dB and 19.53 dB for the algorithm with and without the source separation stage, respectively. Full article

This study proposes a high-contrast photoacoustic (PA) imaging methodology based on a dual-wavelength confocal metalens, designed to monitor the dissemination of cancer cells and to inform subsequent cancer treatment strategies. The metalens is composed of two metasurfaces that perform filtering and focusing functions, effectively reducing the cross-talk between the two wavelengths of light in space and achieving a confocal effect. Furthermore, to minimize process complexity, a uniform material system of silicon dioxide (SiO₂) and titanium dioxide (TiO₂) is employed across the different metasurfaces of the metalens. The designed metalens has a radius of 25 µm and an operational focal length of 98.5 µm. The results confirm that this dual-metasurface design achieves high focusing efficiency alongside precise focusing capability, with the deviations of the actual focal lengths for both beams from the design values being within 1.5 µm. Additionally, this study developed a skin tissue model and simulated multi-wavelength photoacoustic imaging of cancer cells within the human body by integrating theories of radiative transfer, photothermal conversion, and the wave equation. The results demonstrate that the enhancement trend of the reconstructed signal closely matches the original signal, confirming the model’s excellent fitting performance. The sound pressure values generated by cancer cells are significantly higher than those of normal cells, proving that this method can effectively distinguish cancerous tissue from healthy tissue. This research provides new theoretical support and methodological foundations for the clinical application of multi-wavelength photoacoustic imaging technology. Full article

Objective: Molecular biology techniques were employed to investigate the effects of thrombospondin-4 (Thbs4) expression in dorsal root ganglion (DRG) on peripheral nerve injury repair and regeneration, as well as to elucidate the underlying molecular mechanisms. Methods: A sciatic nerve transection model in rat was established to analyze Thbs4 expression and localization in DRG tissues after injury. Both siRNA and adeno-associated virus (AAV) were used to knockdown or overexpress Thbs4. The effects of knockdown and overexpression of Thbs4 on axon growth were assessed using immunofluorescence staining. The roles of Thbs4 in peripheral nerve injury repair and regeneration were determined using behavioral assays, electrophysiological recordings, and transmission electron microscopy. Results: Thbs4 was primarily localized in the cell membrane and cytoplasm of DRG neurons but was also found in the intercellular spaces. In vitro experiments demonstrated that Thbs4 overexpression promoted axonal regeneration and reduced neuronal apoptosis. They also showed that Thbs4 overexpression accelerated sciatic nerve regeneration and enhanced the recovery of motor and sensory functions. Conversely, Thbs4 knockdown had the opposite effects. This study also showed that the knockdown or overexpression of Thbs4 significantly altered the expression of NF-κB and ERK signaling pathways, suggesting their involvement in peripheral nerve repair and regeneration. Conclusions: Thbs4 expression in DRG tissues is significantly altered following sciatic nerve injury. The NF-κB and ERK may be involved in regulating the repair and regeneration of the peripheral nerve by Thbs4. Full article

The signal-processing architecture of passive surface acoustic wave (SAW) sensors presents significant implementation challenges due to its radar-like operational principle and the inherent complexity of discrete component-based hardware design. While System-in-Package (SiP) has demonstrated remarkable success in miniaturizing electronic systems for smartphones, automotive electronics, and IoT applications, its potential for revolutionizing SAW sensor interrogator design remains underexplored. This paper presents a novel architecture that synergistically combines time-domain ADC design with SiP-based miniaturization to achieve unprecedented simplification of SAW sensor readout systems. The proposed time-domain ADC incorporates an innovative delay chain calibration methodology that integrates physical unclonable function (PUF) principles during time-to-digital converter (TDC) characterization, enabling the simultaneous generation of unique system IDs. The experimental results demonstrate that the integrated security mechanism provides variable-length bit entropy for device authentication, and has a reliability of 97.56 and uniqueness of 49.43, with 53.28 uniformity, effectively addressing vulnerability concerns in distributed sensor networks. The proposed SiP is especially suitable for space-constrained IoT applications requiring robust physical-layer security. This work advances the state-of-the-art wireless sensor interfaces by demonstrating how time-domain signal processing and advanced packaging technologies can be co-optimized to address performance and security challenges in next-generation sensor systems. Full article

Magnetic Barkhausen noise (MBN) analysis is a non-destructive evaluation technique that offers significant advantages in assessing the magnetic properties of electrical steels. It is particularly useful for quality control in electrical steel production and for evaluating magnetic quality during core manufacturing and assembly. Despite its potential, MBN has not been widely used in electrical steel characterization. One obstacle is that the effects of silicon content in the electrical steel and the residual stress generated during its processing on MBN have not been thoroughly understood, limiting the practical application of the MBN technique in the electrical steel and electric motor industries. To address this knowledge gap, this paper investigates the MBN responses from four non-oriented electrical steel (NOES) sheets with varying silicon contents (0.88, 1.8, 2.8, and 3.2 wt%) but similar other elements. The measurements were performed both with and without applied tensile stress. It is observed that increasing the Si content increases the pinning density, which, together with the microstructure and texture, largely impacts the MBN response. In addition, the MBN energy increases with the applied stress, which can be attributed to the increase in the number of 180° domain walls (DWs) in the direction of stress. The rate of this MBN increase, however, differs among steels with different silicon concentrations. This difference is due to the combined effect of the DWs and pinning density. When the DW spacing becomes less than the jump distance between the pinning sites, no further increase in the MBN energy is observed with additional stress. The reported results provide a basis for the interpretation of MBN signals for varying wt% Si in NOES when residual stresses are present. Full article

Astronauts on the proposed Mars missions will be exposed to extended periods of social isolation (SI) and space radiation (SR). SI and SR-induced immune dysregulation can result in persistent neuroinflammation and neuronal damage which could negatively impact an astronaut’s health and ability to maintain adequate levels of performance. The synergistic effects of combined SI and SR on immune system functionality and the brain remain unknown. Determining how single and combined inflight stressors modulate the immune system is crucial for fully understanding pathways impacting astronaut health and performance. We used ground-based analogs of SI and SR in rodent models to investigate how SI and SR, and their combination (dual flight stressors (DFS)), impact immune cell recruitment into the brain and alter gene expression related to immune signaling and neuroinflammation. We also assessed whether putative phenotypic differences in stress resilience and vulnerability were reflected in neuroinflammatory-related gene expression. SI rats exhibited differences in neuroinflammatory signaling but no differences in infiltrating cells compared to Controls. SR rats exhibited up-regulated gene expression related to cytokine signaling and immune cell recruitment and unexpectedly depleted infiltrating immune cells. Many deficits related to the immune response in the SR animals were attenuated by dual exposure to SI. These data demonstrate significant differences in the effects of spaceflight stressors on immune function and how they may vary with individual stress resilience and vulnerability. Full article

Current Satellite-Based Augmentation Systems (SBASs) improve the positioning accuracy and integrity of GPS satellites and provide safe civil aviation navigation services for procedures from en-route to LPV-200 precision approach over specific regions. SBAS systems, such as WAAS, EGNOS, GAGAN, and MSAS, already operate. The development of operational SBAS systems is in transition due to the extension of L1 SBAS services to new regions and the improvements expected by the introduction of dual frequency multi-constellation (DFMC) services, which allow the use of more core constellations such as Galileo and the use of ionosphere-free L1/L5 signal combination. The UKSBAS Testbed is a demonstration and feasibility project in the framework of ESA’s Navigation Innovation Support Programme (NAVISP), which is sponsored by the UK’s HMG with the participation of the Department for Transport and the UK Space Agency. UKSBAS Testbed’s main objective is to deliver a new L1 SBAS signal in space (SIS) from May 2022 in the UK region using Viasat’s Inmarsat-3F5 geostationary (GEO) satellite and Goonhilly Earth Station as signal uplink over PRN 158, as well as L1 SBAS and DFMC SBAS services through the Internet. SBAS messages are generated by GMV’s magicSBAS software and fed with data from the Ordnance Survey’s station network. This paper provides an assessment of the performance achieved by the UKSBAS Testbed during the last two years of operations at the SIS and user level, including a number of experimentation campaigns performed in the aviation and maritime domains, comprising ground tests at airports, flight tests on aircraft and sea trials on a vessel. This assessment includes, among others, service availability (e.g., APV-I, LPV-200), protection levels (PL), and position errors (PE) statistics over the service area and in a network of receivers. Full article

In the new energy electric drive system, the thermal stability of IGBT, a core power device, significantly impacts the system’s overall performance. Accurate IGBT temperature measurement is crucial, but traditional methods face limitations in IGBT’s compact working space. Thin-film thermocouples, with their thin and light features, offer a new solution. In this study, Ni 90% Cr 10% and Ni 97% Si 3% thin-film thermocouples were prepared on polyimide substrates via magnetron sputtering. After calibration, the Seebeck coefficient of the thin-film thermocouple temperature sensors reached 40.23 μV/°C, and the repeatability error stabilized at about 0.3% as the temperature rose, showing good stability. Researchers studied factors affecting IGBT temperature. Thin-film thermocouples can accurately monitor IGBT module surface temperature under different conditions. Compared to K-type wire thermocouples, they measure slightly higher temperatures. As the control signal’s switching frequency increases, IGBT temperature first rises then falls; as the duty cycle increases, the temperature keeps rising. This is consistent with RAC’s junction temperature prediction theory, validating the feasibility of thin-film thermocouples for IGBT chip temperature measurement. Thin-film thermocouples have great application potential in power device temperature measurement and may be a key research direction, supporting the optimization and upgrading of new energy electric drive systems. Full article

Satellites traversing highly elliptical orbits (HEOs) encounter more severe radiation effects caused by the space particle environment, which are distinct from those in a low Earth orbit (LEO), medium Earth orbit (MEO), and geostationary orbit (GEO). This study proposed a space environment detection payload technology for assessing the particle radiation environment in HEOs. During ground tests, all technical indicators of the detection payload were calibrated and verified using reference signal sources, standard radioactive sources, and particle accelerators. The results indicate that the space environment detection payload can detect electrons and protons within the energy ranges of 30 keV to 2.0 MeV and 30 keV to 300 MeV, respectively, with an accuracy greater than 10%. The detection range of the surface potential spans from −11.571 kV to +1.414 kV, with a sensitivity greater than 50 V. Furthermore, the radiation dose detection range extends from 0 to 3.38 × 10⁶ rad (Si), with a sensitivity greater than 3 rad (Si). These indicators were also validated through an in-orbit flight. The observation of the particle radiation environment, radiation dose accumulation, and satellite surface potential variation in HEOs can cover space areas that have not been addressed before. This research helps fill the gaps in China’s space environment data and promotes the development of a space-based environment monitoring network. Full article

Heavy ion radiation, prevalent in outer space and relevant for radiotherapy, is densely ionizing and poses a risk to intestinal stem cells (ISCs), which are vital for maintaining intestinal homeostasis. Earlier studies have shown that heavy-ion radiation can cause chronic oxidative stress, persistent DNA damage, cellular senescence, and the development of a senescence-associated secretory phenotype (SASP) in mouse intestinal mucosa. However, the specific impact on different cell types, particularly Lgr5⁺ intestinal stem cells (ISCs), which are crucial for maintaining cellular homeostasis, GI function, and tumor initiation under genomic stress, remains understudied. Using an ISCs-relevant mouse model (Lgr5⁺ mice) and its GI tumor surrogate (Lgr5⁺Apc^1638N/+ mice), we investigated ISCs-specific molecular alterations after high-LET radiation exposure. Tissue sections were assessed for senescence and SASP signaling at 2, 5 and 12 months post-exposure. Lgr5+ cells exhibited significantly greater oxidative stress following ²⁸Si irradiation compared to γ-ray or controls. Both Lgr5⁺ cells and Paneth cells showed signs of senescence and developed a senescence-associated secretory phenotype (SASP) after ²⁸Si exposure. Moreover, gene expression of pro-inflammatory and pro-growth SASP factors remained persistently elevated for up to a year post-²⁸Si irradiation. Additionally, p38 MAPK and NF-κB signaling pathways, which are critical for stress responses and inflammation, were also upregulated after ²⁸Si radiation. Transcripts involved in nutrient absorption and barrier function were also altered following irradiation. In Lgr5⁺Apc^1638N/+ mice, tumor incidence was significantly higher in those exposed to ²⁸Si radiation compared to the spontaneous tumorigenesis observed in control mice. Our results indicate that high-LET ²⁸Si exposure induces persistent DNA damage, oxidative stress, senescence, and SASP in Lgr5⁺ ISCs, potentially predisposing astronauts to altered nutrient absorption, barrier function, and GI carcinogenesis during and after a long-duration outer space mission. Full article

Underwater wireless sensor networks play an important role in exploring the oceans as part of an integrated space–air–ground–ocean network. Because underwater energy is limited, the equipment’s efficiency is significantly impacted by the battery duration. Underwater backscatter technology does not require batteries and has significant potential in positioning, navigation, communication, and sensing due to its passive characteristics. However, underwater backscatter signals are susceptible to being swamped by the excitation signal. Additionally, the signals from different reflection signals share the same frequency and overlap, and contain fewer useful features, leading to significant challenges in detection. In order to solve the above problems, this paper proposes a recurrent neural network that introduces time-frequency and reference signal features for underwater backscatter signal separation (TF-REF-RNN). In the feature extraction part, we design an encoder that introduces time-frequency domain features to learn more about the frequency details. Additionally, to improve performance, we designed a separator that incorporates the reference signal’s pure global information features. The proposed TF-REF-RNN network model achieves metrics of 28.55 dB SI-SNRi and 19.51 dB SDRi in the dataset that includes shipsEar noise data and underwater simulated backscatter signals, outperforming similar classical methods. Full article

Laser surface remelting of aluminum alloys has emerged as a promising technique to enhance mechanical properties through refined microstructures. This process involves rapid cooling rates ranging from 10³ to 10⁸ °C/s, which increase solid solubility within aluminum alloys, shifting their eutectic composition to a larger value of silicon content. Consequently, the resulting microstructure combines a strengthened aluminum matrix with silicon fibers. This study focuses on the laser scanning of Al-Si aluminum alloy to reduce the size of aluminum matrix spacings and transform fibrous silicon particles from micrometer to nanometer dimensions. Analysis revealed that the eutectic structure contained 17.55% silicon by weight, surpassing the equilibrium eutectic composition of 12.6% silicon. Microstructure dimensions within the molten zones, termed ‘melt pools’, were extensively examined using Scanning Electron Microscopy (SEM) at intervals of approximately 20 μm from the surface. A notable increase in hardness, exceeding 50% compared to the base plate, was observed in the melt pool regions. Thus, it is exemplified that laser surface remelting introduces a novel strengthening mechanism in the alloy. Moreover, this study develops an in situ method for predicting melt pool properties and dimensions. A predictive model is proposed, correlating energy density and spectral signals emitted during laser remelting with mechanical properties and melt pool dimensions. This method significantly reduces characterization time from days to seconds, offering a streamlined approach for future studies in additive manufacturing. Full article

Thanks to advancements in silicon photomultiplier sensors (SiPMs) and system-on-chip (SoC) technology, our INFN Roma1 group developed ArduSiPM in 2012, the first all-in-one scintillator particle detector in the literature. It used a custom Arduino Due shield to process fast signals, utilizing the Microchip Sam3X8E SoC’s internal peripherals to control and acquire SiPM signals. The availability of radiation-tolerant SoCs, combined with the goal of reducing system space and weight, led to the development of an innovative second-generation board, a better-performing device called Cosmo ArduSiPM, suitable for space missions. The architecture of the new detector is based on the Microchip SAMV71 300 MHz, 32-bit ARM^® Cortex^®-M7 (Microchip Technology Inc., Chandler, AZ, USA). While the analog front-end is essentially identical to the ArduSiPM, it utilizes components with the smallest possible package. The board fits in a CubeSat module. Thanks to the compact design, the board has two independent channels, with a total weight of only 40 grams within a CubeSat form factor. The ArduSiPM architecture is based on a single microcontroller and fast discrete analog electronics. It benefits from the continued development of SoCs related to the IoT (Internet of Things) market. Compared with a system with a custom ASIC, this architecture based on software and SoC capabilities offers considerable advantages in terms of cost and development time. The ability to incorporate new commercial SoCs, continuously emerging from advancements in the aerospace and automotive industries, provides the system with a robust foundation for sustained growth over the years. A detailed characterization of the hardware and the system’s response to different photon fluxes is presented in this article. Additionally, coupling the device with a scintillator was tested at the end of this article as a preliminary trial for future measurements, showing potential for further enhancement of the detector’s capabilities. Full article

High diffraction signal-to-background ratios (SBRs), the ratio of diffraction peak integrated intensity over its background intensity, are desirable for a neutron diffractometer to acquire good statistics for diffraction pattern measurements and subsequent data analysis. For a given detector, while the diffraction peak signals primarily depend on the characteristics of the neutron beam and sample coherent scattering, the background largely originates from the sample incoherent scattering and the scattering from the instrument space. In this work, we investigated the effect of collimation on neutron diffraction SBRs of Si powder measurements using one high-angle area detector bank coupled with six different collimation configurations in a large and complex instrument space at the engineering materials diffractometer VULCAN, SNS, ORNL. The results revealed that the diffraction SBRs can be significantly improved by a proper coarse collimator that leaves no gap between the detector and the collimator, and the improvement of SBRs by a fine radial collimator was remarkable with a proper coarse collimator in place but not distinguishable without one. It was also found that the diffraction SBRs were not effectively improved by adding the neutron-absorbing element boron to the fine radial collimator body, which indicates that either the absorption of secondary scattered neutrons by the added boron is insignificant or the collimator base material (resin and ABS) alone attenuates background scattering sufficiently. These findings could serve as a useful reference for diffractometer developers and/or operators to optimize their collimation to achieve higher diffraction SBRs. Full article